Apparatus for grinding wood-pulp.



PATENTED JAN. 7. 1908.

2 SHEEIS-SHBET- 1.

K.GEVERS. APPARATUS FOR GRINDING WOOD PULP.

APPLICATION FILED SEPT 19 1906 UNITED STATES PATENT i OFFICE.

KARL GEVERS, OF OSTERODE-IN-THE-HARZ, GERMANY APPARATUS FOR GRINDING WOOD-PULP.

Specification of Letters Patent.

Patented Jan. 7, 1908.

- Application filed September 19. 1906. Serial No. 335,313.

pulp or cellulose, and the essential part of the.

improvement consists in grinding the wood under a jet of water, on a grind stone provided with a horizontal spindle, until it be-.

comes of the consistency of thick soup.

Hitherto in the grinding of wood, a stone with comparatively flat grinding surfaces has been used, that is to say a stone with comparatively small indentations on it and on such a stone the Wood has been ground to wood pulp with the addition of a large quantity of water. Such fiat grinding surfaces attack the wood in such a way that the-particles of cellulose are not separated from the wood in the most favorable manner but are torn out of it and rolled oil it, the effect of the pressure being that the ligneous-cells' are destroyed and, in the case of pine and other needle woods, the resin in'the cells also is destroyed and washed away by the large volume of water supplied. In every case the result is a non-uniform material of low value, which, owing to the high proportion of water it contains, requires considerable subsequent drying. In addition to this, when a grind stone is sharpened, according to the old method, the guides for the wood (71. e., the smooth parts formed on the grind stone by wear, which parts carry the wood that is pressed .against them) are not sufliciently protected and saved, the edges of the teeth break off and the stone becomes uneven on its grinding surface with the result that it prejudicially affects the grinding and the product.

' The disadvantages above described are obviated in the resent invention mainly for the reason that the ground material on the stone is damped with only 10 parts of water, shortly after it has been ground and that the water is played .on-it through a rose pipe in order-to more easily loosen the portions of the material adherin to the stone. The water passes round t e lower part of the stone and out of the trough or box at the end opposite the rose jet, at a point-at or about the same level as the horizontal spindle of the stone, and thence over a bent partition. In this way a Wood pulp of uniform consistency is produced containing only 10 parts of water and which does not squirt or splash over the sides of the trough. Before it leaves the trough this wood pulp forms the so called Fangbrei or catching liquor which as it travels round the lower part of the stone before leaving the trough draws the particles of the material out of the depressions in the stone which latter is therefore kept clean and dry on its upper side so that its sharpened depressions can, under the action of the press, fill with fresh wood grindings. In this way a dry grinding is rendered possible.

Thewood pulp as it leaves the grinding stone does not require to be dried owing to the small quantity of water it contains and the material can easily be sorted for immediate use in paper machines or pulp machines. In addition there is the further advantage of economyin power, owing to the considerably less pressure required in the press. These advantages are due in reat measure to the use of larger sharpened depressions, which give large grinding surfaces on the stone. As a result, the stone acts rather by scraping than by tearing, and the ground wood produced is better in quality, as it retains the long cells which favor its felting qualities. The ground wood obtained according to this dry grinding process contains no refining material and few fibers, so that it can be used after being simply sorted. In order to obtain an extremely fine, soft and, binding material with. numerous cells, isolated but entire, in which the natural resin of needle wood is retained uninjured, the grinding surface, which has on it extraordinarily large depressions, is covered over with a small quantity of metallic lead, after being sharpened, in order to secure proper guidance for the wood. This lead saves the stone at the beginning of the as it protects the same and sharp edges being broken off.

On the appended drawing one arrangement of ap aratus for carrying out the process is clearly represented.

Figure 1 is a view partly in vertical seetionan'dpartly in elevationiFig. 2 is an prevents the rinding action enlarged section as on the'line 2-2 of Fig. 3.

' there is a row of fiat depressions i formed in the stone. The purpose of these depressions is to give the'stone greater durability in the deep part and to compensate for the self sharpening power which would otherwise greatly be diminished owing to small fragments getting broken off. The smooth grains of sand embedded in the quartz of the cutters will effect the guiding of the wood. This critical period after sharpening is now ot over by partially coating or coverin with lead is as above mentioned. The lea preferably runs obliquely from the side to the shaft of the stone, in the direction shown by arrows, some of it being thus caused to adhere to the corresponding cutting edges of the notches h or 1', over the whole circumference of the stone, at intervals of about 10 to 15 centimeters approximately, so that too much lead is not ap lied to the stone. The lead is distributed fly the rinding process and adheres to the stone, rent ering it smooth, until a sufficient degree of smoothness has again been reduced automatically in the stone itself.

The material ground off the wood I), on the stone a (which revolves in the direction of the arrow) is moistened immediately after it is ground off by playing on it through a rose pipe only 10 parts of water. The wood is pressed, in the usual manner, against the stone a by means of a piston or the like work ing in the casing. The Fangbrei or catchin liquor formed out of the ground is retained by a trough e which partly envelops the stone, or by a curved partition wall d. The liquor passes up the trough and out thereof at or about the level of the horizontal spindle of the stone, in the neighborhood off into a receiver g.

The stone a which effects the grinding has a surface provided with very sharp cutting edges, produced by extremely large depi'essions made in it, and between these there is a series of flat cuts, entering into the stone. The purpose of these latter is to make the stone more resisting and'durable in the deep cuts and to compensate for the gradual diminution of the self-sharening, which results from the breaking o of fragile particles. The smooth grains of sand, bedded in the form of quartz, on the cutting edges, which v are rotected by the layer of lead, serve to gui e the wood.

The lar e depressions in the stone, which may suita bly be made of pyramidal shape, produce broad grinding surfaces, which act on the wood more by rubbing than by catching into it or tearing it.

The product obtained is an extremely fine, soft, and binding material, the cells of which are for the most part uninjured. The material is so thickthat it can be immediately pressed or treated in a centrifugal machine to make it ready for transport, and the drying in order to free it from water, hitherto necessary, can be dispensed with. The ma terial may be pressed in heaps and kept for a long time without being destroyed. The paper or the pulp made from this material is distinguished by toughness and uniform smoothness.

The thick pulpy material moving in the trough 2 draws any material adhering to the stone out of the depressions thereof so that they can be filled again with newly ground wood.

With respect to the preparation of the grinding surface of the stone,- the following further points must be noted. The guides, that is to say the smooth surfaces between the sharp ridges on the stone, form themselves without aid but the maintenance of them in a proper condition, notwithstanding their great sharpness, is the essential preliminary condition for the success of the present process, for, if the stone is overworked only at certain points, that is to say, if it loses the power to guide the wood, the total result is of little value, the product being non-uniform and bad.

The wear on a sharpening hammer or on the steel plates used, on a soft sand-stone is very considerable. If one set of blades be used for the whole stone, it can be clearly seen that the stone must be sharpened in an irregular fashion, for sharp implements are used to begin with, but blunted implements later on. The consequence of this is that the wood is subjected to shocks and blows,owing to the unequally sharpened attacking surfaces of the stone. At the commencement the section of the stone sharpened with the blunted steel will attack the wood more powerfully than the portion that has been treated with sharp tools, because the latter will leave a larger gliding surface on the stone. After each operation of sharpening there is a critical period, which is quite independent of the style of sharpening. It is brought about by the small particles of stone working loose in the operation. These articles deprive the stone of the smooth surace left on it when it was sharpened, and produce irregularities in the process of grinding, which irregularities may continue for a very long time. This critical period is now got over by covering with lead, as above mentioned, after sharpening. The lead adheres to the stone for a long enough time to allow of sufficiently smooth surfaces forming naturally'on the stone again.

With very sharp teeth, deep and large openings are made in the stone, and through this particular method of sharpening the smoothness or guiding power is saved. The stone is deprived of this guiding power in proportion to the bluntness of the hammer.

To prevent the stone breaking off where it is cut deep, the sharp steel tooth-plates are fixed at varying depths, row after row so that one row of teeth will cut in deep while another row will not enter so far into the surface of the stone. The proportionately large holes on the stone intended 'for use in the resent process take up the material that has een freshly ground off and afford roomfor it, so that it can be detached Without any catching into the wood or tearing it off. These also render it possible for the elastic wood to form into wide and large surfaces which, under the microscope, show flat wide and fine formations of cells.

Another advantage is found in the present method of sharpening, in that the stone adj usts itself automatically during the grinding and maintains its round form notwithstanding differences in hardness. In this way knocks and shocks that would soon wear out the stone, notwithstanding its great sharpness, are avoided.

Having now fully described my invention what I claim and desire to secure by Letters Patent is 1. Apparatus for grinding wood in the manufacture of wood pulp or cellulose comprising, in combination, a grind stone, means for pressing the wood against the surface of the grind stone and a water ipe adapted to deliver a water spray on on y the ground material carried by the stone as the latter revolves, said pipe being disposed to discharge at substantially the horizontal axis of the stone and provision for cleaning the lower surface of the stone by delivering the water at a point atsubstantially the plane of its horizontal axis.

2. Apparatus for grinding wood in the manufacture of wood pulp or cellulose, comprising, in combination, a receiver, a grind stone mounted in the receiver, means for pressing the wood against the upper surface of the stone, a water pipe having a rose there on for spraying water in a downward direction upon the ground material only at sub stantially the plane of its horizontal axis to keep the lower surface of the stone clean, and a guide in the receiver for directing the water and pulp around the lower part of the stone and up to a position in line with the axis thereof.

3. Apparatus for grinding wood in the manufacture of wood pulp or cellulose comprising, in combination, a receiver, a revoluble grind stone with deep indentations on its surface mounted in said receiver, means for pressing the wood against the upper surface of the grind stone, a water pipe with rose arranged at one side of the grind stone and adapted to deliver a spray of water in a downwardly inclined direction on the ground material only at and after it passes the horizontal center of the stone and a trough with curved bottom in the receiver said trough being carried up to a position in line with the axle of the grind stone.

4. Apparatus for grinding wood in the manufacture of wood pulp or cellulose comprising, in combination, a receiver, a revoluble grind stone therein having deep indentations covered with metallic lead on its surface, means for pressing the wood against the upper surface of the grind stone, a water pipe with rose arranged at one side of the grind stone, and adapted to deliver a spray of wa ter in a downwardly inclined direction on the ground material only at and after it passes the horizontal center of the stone, and a trough with a curved bottom in the receiver said trough being imperforate and concentric with the stone and carried up to a position in line with the grind stone, whereby the ground material is automatically cleaned from the lower surface of the grindstone and a substantially clean and dry upper side is presented to the material to be ground.

In testimony whereof I aflix my signature in presence of two witnesses.

KARL GEVERS.

Witnesses WOLDEMAR I'IAUPTQJ HENRY HASPER. 

